The present invention relates to thermosetting resin compositions and uses therefor. In a particular aspect, the present invention relates to thermosetting resin compositions containing maleimide resins, vinyl resins, or both.
Bismaleimides per se occupy a prominent position in the spectrum of thermosetting resins. Indeed, several bismaleimides are commercially available. Bismaleimide resins are used as starting materials for the preparation of thermoset polymers possessing a wide range of highly desirable physical properties. Depending on the particular resin and formulation, the resins provide cured products having excellent storage stability, heat resistance, as well as good adhesive, electrical and mechanical properties. Accordingly, bismaleimide resins have been used for the production of moldings, heat-resistant composite materials, high temperature coatings and for the production of adhesive joints. Typically, however, in any particular resin formulation there is a trade-off between the various properties. For example, in the formulation of xe2x80x9csnapxe2x80x9d cure adhesives (i.e., adhesives that cure in two minutes or less at xe2x89xa6200xc2x0 C.), it is desirable to use a system which does not require the addition of diluent to facilitate handing. In other words, snap cure products require formulations containing 100% reactive materials. Thus, it is desirable to prepare snap cure resins which are liquid at or about room temperature (i.e., low viscosity materials) for ease of handling.
Unfortunately, up until now, it has not proved possible to formulate bismaleimide compositions that are both quick curing, easy to handle (i.e., liquid at or about room temperature), and have low moisture uptake. Consequently, it is a desideratum to provide thermosetting bismaleimide resin compositions that produce cured resins exhibiting a combination of highly desirable physical properties, including a combination of rapid curing and low water absorption.
A particular disadvantage of the use of bismaleimide resins for the types of applications described above is that, at room temperature, such materials exist as solid resins which require the addition of liquid diluents, in order for such resins to achieve a useful and processable viscosity. This difficulty has been compounded by the poor solubility of bismaleimides in organic solvents. This poor solubility generally necessitates the use of polar diluents, such as N-methyl-2-pyrrolidone or dimethylformamide. These diluents are undesirable, inter alia, from the viewpoint of environmental pollution. Therefore, it is another desideratum to provide bismaleimide resins that require little, if any, non-reactive diluent to facilitate handling.
One approach to solving the problem of a need for a diluent has been to use reactive liquid diluents. For example, the co-cure of simple bismaleimides with relatively simple divinyl ethers is known in the art. The use of such diluents is advantageous in that these materials become incorporated into the thermosetting resin composition, and hence do not create disposal problems. However, the range of suitable liquid reactive diluents is very limited. Many of the available diluents are restricted by the low boiling points thereof, and, therefore, the high volatility thereof; by the odor of such materials; by the toxicity of such materials and/or problems with skin irritation induced thereby; by the poor ability of such materials to solubilize bismaleimides; by the high viscosity of such materials, which, again, limits the bismaleimide solubility and also leads to little or no tack in the formulation; by the poor thermal stability and/or hydrolytic stability of such materials; by the incompatibility of such materials with other formulation modifiers, and the like. In particular, since the diluents become an integral component of the thermosetting resin composition, they necessarily influence its properties. Consequently, it is another desideratum to provide combinations of bismaleimide resins with reactive diluents which do not suffer from the above-described drawbacks and that produce cured resins exhibiting a combination of highly desirable physical properties, including rapid curing and low water absorption.
Accordingly, there has existed a definite need for bismaleimide resins that produce cured resins exhibiting a combination of highly desirable physical properties, including rapid curing and low water absorption. There has existed a further need for bismaleimide resins that require the additions of little, if any, non-reactive diluent to facilitate handling. And there has existed a still further need for combinations of bismaleimide resins with reactive diluents which do not suffer from the limitations of known reactive resins and that produce cured resins exhibiting a combination of highly desirable physical properties, including rapid curing and low water absorption. The present invention satisfies these and other needs and provides further related advantages.
In accordance with the present invention, we have developed novel thermosetting resin compositions which meet all of the above-described needs, i.e., produce cured resins exhibiting a combination of highly desirable physical properties, including rapid curing and low water absorption, and which require little, if any, diluent to provide a system of suitable viscosity for convenient handling. In another aspect of the invention, we have developed novel combinations of bismaleimide resins with reactive diluents, which do not suffer from the limitations of known reactive resins and that produce cured resins exhibiting a combination of highly desirable physical properties, including rapid curing and low water absorption. The resulting cured resins are stable at elevated temperatures, are highly flexible, have low moisture uptake and good adhesion.
In accordance with the present invention, there are provided novel maleimide resins of general formula I, as follows: 
wherein:
m=1, 2 or 3,
each R is independently selected from hydrogen or lower alkyl, and
X is a monovalent or polyvalent radical selected from:
high molecular weight branched chain alkyl, alkylene or alkylene oxide species having from about 12 to about 500 atoms in the backbone thereof,
aromatic groups having the structure: 
wherein:
n=1, 2 or 3,
each Ar is a monosubstituted, disubstituted or trisubstituted aromatic or heteroaromatic ring having in the range of 3 up to 10 carbon atoms, and
Z is a high molecular weight branched chain alkyl, alkylene or alkylene oxide species having from about 12 to about 500 atoms in the backbone thereof,
as well as mixtures thereof.
It is a distinct advantage of the bismaleimide resins of Formula I that they can be used with little, if any, added diluent. Generally, for easy handling and processing, the viscosity of a thermosetting resin composition must fall in the range of about 10 to about 12,000 centipoise, preferably from about 10 to about 2,000 centipoise. Maleimide resins of Formula I typically require no added diluent, or when diluent is used with resins contemplated by Formula I, far less diluent is required to facilitate handling than must be added to conventional maleimide-containing thermosetting resin systems. Preferred maleimide resins of Formula I include stearyl maleimide, oleyl maleimide and behenyl maleimide, 1,20-bismaleimido-10,11-dioctyl-eicosane (which likely exists in admixture with other isomeric species produced in the ene reactions employed to produce dimer acids from which the bismaleimide is prepared, as discussed in greater detail below), and the like, as well as mixtures of any two or more thereof.
When a diluent is added, it can be any diluent which is inert to the bismaleimide resin and in which the resin has sufficient solubility to facilitate handling. Representative inert diluents include dimethylformamide, dimethylacetamide, N-methylpyrrolidone, toluene, xylene, methylene chloride, tetrahydrofuran, methyl ethyl ketone, monoalkyl or dialkyl ethers of ethylene glycol, polyethylene glycol, propylene glycol or polypropylene glycol, glycol ethers, and the like.
Alternatively, the diluent can be any reactive diluent which, in combination with bismaleimide resin, forms a thermosetting resin composition. Such reactive diluents include acrylates and methacrylates of monofunctional and polyfunctional alcohols, vinyl compounds as described in greater detail herein, styrenic monomers (i.e., ethers derived from the reaction of vinyl benzyl chlorides with mono-, di-, or trifunctional hydroxy compounds), and the like.
Now in accordance with the invention there has been found an especially preferred class of reactive diluents corresponding to vinyl or polyvinyl compounds having the general formula: 
wherein:
q is 1, 2 or 3,
each R is independently as defined above,
each Q is independently selected from xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94C(O)xe2x80x94, xe2x80x94C(O)xe2x80x94 or xe2x80x94C(O)xe2x80x94Oxe2x80x94, and
Y is selected from:
saturated straight chain alkyl, alkylene or alkylene oxide, or branched chain alkyl, alkylene or alkylene oxide, optionally containing saturated cyclic moieties as substituents on said alkyl, alkylene or alkylene oxide chain or as part of the backbone of the alkyl, alkylene or alkylene oxide chain, wherein said alkyl, alkylene or alkylene oxide species have at least 6 carbon atoms, preferably wherein said alkyl, alkylene or alkylene oxide species are high molecular weight branched chain species having from about 12 to about 500 carbon atoms,
aromatic moieties having the structure: 
wherein each R is independently as defined above, Ar is as defined above, t falls in the range of 2 up to 10, and u is 1, 2 or 3,
polysiloxanes having the structure:
xe2x80x94(CR2)mxe2x80x2xe2x80x94[Si(Rxe2x80x2)2xe2x80x94O]qxe2x80x2xe2x80x94Si(Rxe2x80x2)2xe2x80x94(CR2)nxe2x80x2xe2x80x94
wherein each R is independently defined as above, and each Rxe2x80x2 is independently selected from hydrogen, lower alkyl or aryl, mxe2x80x2 falls in the range of 1 up to 10, nxe2x80x2 falls in the range of 1 up to 10, and qxe2x80x2 falls in the range of 1 up to 50,
polyalkylene oxides having the structure:
xe2x80x94[(CR2)rxe2x80x94Oxe2x80x94]qxe2x80x2xe2x80x94(CR2)sxe2x80x94
wherein each R is independently as defined above, r falls in the range of 1 up to 10, s falls in the range of 1 up to 10, and qxe2x80x2 is as defined above,
as well as mixtures of any two or more thereof.
Exemplary vinyl or polyvinyl compounds embraced by the above generic structure include stearyl vinyl ether, behenyl vinyl ether, eicosyl vinyl ether, isoeicosyl vinyl ether, isotetracosyl vinyl ether, poly(tetrahydrofuran) divinyl ether, tetraethylene glycol divinyl ether, tris-2,4,6-(1-vinyloxybutane-4-)oxy-1,3,5-triazine, bis-1,3-(1-vinyloxybutane-4-)oxycarbonyl-benzene (alternately referred to as bis (4-vinyloxybutyl)isophthalate; available from Allied-Signal Inc., Morristown, N.J., under the trade name Vectomer(trademark) 4010), divinyl ethers prepared by transvinylation between lower vinyl ethers and higher molecular weight di-alcohols (e.g., xcex1,xcfx89-dihydroxy hydrocarbons prepared from dimer acids, as described above; an exemplary divinyl ether which can be prepared from such dimer alcohols is 10,11-dioctyl eicosane-1,20-divinyl ether, which would likely exist in admixture with other isomeric species produced in ene reactions employed to produce dimer acids), in the presence of a suitable palladium catalyst (see, for example, Example 9), optionally hydrogenated xcex1,xcfx89-disubstituted polybutadienes, optionally hydrogenated xcex1,xcfx89-disubstituted polyisoprenes, optionally hydrogenated xcex1,xcfx89-disubstituted poly[(1-ethyl)-1,2-ethane], and the like. Preferred divinyl resins include stearyl vinyl ether, behenyl vinyl ether, eicosyl vinyl ether, isoeicosyl vinyl ether, poly(tetrahydrofuran) divinyl ether, divinyl ethers prepared by transvinylation between lower vinyl ethers and higher molecular weight di-alcohols (e.g., xcex1,xcfx89-dihydroxy hydrocarbons prepared from dimer acids, as described above; an exemplary divinyl ether which can be prepared from such dimer alcohols is 10,11-dioctyl eicosane-1,20-divinyl ether, which would likely exist in admixture with other isomeric species produced in ene reactions employed to produce dimer acids), in the presence of a suitable palladium catalyst (see, for example, Example 9), and the like.
Additionally, in accordance with another embodiment of the present invention, it has been found that divinyl compounds corresponding to Formula II where -Q- is xe2x80x94C(O)xe2x80x94Oxe2x80x94 and Y is a high molecular weight branched chain alkylene species having from about 12 to about 500 carbon atoms are useful thermosetting resin compositions, even in the absence of bismaleimide resins. When combined with suitable amounts of at least one free radical initiator and at least one coupling agent, these divinyl ether resins, alone, are capable of forming thermosetting resin compositions exhibiting excellent physical properties, including rapid cure rates and low water absorption.
In accordance with yet another embodiment of the present invention, there are provided thermosetting resin compositions made of mixtures of a vinyl compound of Formula II and a maleimide corresponding to the following general formula (generally containing in the range of about 0.01 up to about 10 equivalents of vinyl compound per equivalent of maleimide with in the range of about 0.01 up to about 1 eq. being preferred where the vinyl compound is a mono- or polyvinyl ether): 
wherein:
m is as defined above,
each R is independently as defined above, and
Xxe2x80x2 is a monovalent or polyvalent radical selected from:
saturated straight chain alkyl or alkylene, or branched chain alkyl or alkylene, optionally containing saturated cyclic moieties as substituents on said alkyl or alkylene chain or as part of the backbone of the alkyl or alkylene chain, wherein said alkyl or alkylene species have at least 6 carbon atoms, preferably wherein said alkyl or alkylene species are high molecular weight branched chain species having from about 12 to about 500 carbon atoms,
aromatic groups having the structure: 
wherein
n is as defined above, Ar is as defined above, and Zxe2x80x2 is a monovalent or polyvalent radical selected from:
saturated straight chain alkyl or alkylene, or branched chain alkyl or alkylene, optionally containing saturated cyclic moieties as substituents on said alkyl or alkylene chain or as part of the backbone of the alkyl or alkylene chain, wherein said species have at least 6 carbon atoms, preferably wherein said species are high molecular weight branched chain species having from about 12 to about 500 atoms as part of the backbone thereof,
siloxanes having the structure:
xe2x80x94(CR2)mxe2x80x2xe2x80x94[Si(Rxe2x80x2)2xe2x80x94O]qxe2x80x94Si(Rxe2x80x2)2xe2x80x94(CR2)nxe2x80x2xe2x80x94
wherein each R and Rxe2x80x2 is independently defined as above, and wherein each of mxe2x80x2, nxe2x80x2 and q is as defined above,
polyalkylene oxides having the structure:
xe2x80x94[(CR2)rxe2x80x94Oxe2x80x94]qxe2x80x2xe2x80x94(CR2)sxe2x80x94
wherein each R is independently as defined above, and wherein each of r, s and qxe2x80x2 is as defined above,
aromatic moieties having the structure: 
wherein each R is independently as defined above, Ar is as defined above, and each of t and u is as defined above,
siloxanes having the structure:
xe2x80x94(CR2)mxe2x80x2xe2x80x94[Si(Rxe2x80x2)2xe2x80x94O]qxe2x80x94Si(Rxe2x80x2)2xe2x80x94(CR2)nxe2x80x2xe2x80x94
wherein each R and Rxe2x80x2 is independently defined as above, and wherein each of mxe2x80x2, nxe2x80x2 and qxe2x80x2 is as defined above,
polyalkylene oxides having the structure:
xe2x80x94[(CR2)rxe2x80x94Oxe2x80x94]qxe2x80x2xe2x80x94(CR2)sxe2x80x94
wherein each R is independently as defined above, and wherein each of r, s and qxe2x80x2 is as defined above,
as well as mixtures of any two or more thereof.
Such mixtures possess a combination of highly desirable physical properties, including both rapid cure rates and low water absorption.
Exemplary bismaleimides embraced by Formula III include bismaleimides prepared by reaction of maleic anhydride with dimer amides (i.e., xcex1,xcfx89-diamino hydrocarbons prepared from dimer acids, a mixture of mono-, di- and tri-functional oligomeric, aliphatic carboxylic acids; dimer acids are typically prepared by thermal reaction of unsaturated fatty acids, such as oleic acid, linoleic acid, and the like, which induces an ene reaction, leading to the above-mentioned mixture of components). An exemplary bismaleimide which can be prepared from such dimer amides is 1,20-bismaleimido-10,11-dioctyl-eicosane, which would likely exist in admixture with other isomeric species produced in the ene reactions employed to produce dimer acids. Other bismaleimides contemplated for use in the practice of the present invention include bismaleimides prepared from xcex1,xcfx89-aminopropyl-terminated polydimethyl siloxanes (such as xe2x80x9cPS510xe2x80x9d sold by Hxc3xcls America, Piscataway, N.J.), polyoxypropylene amines (such as xe2x80x9cD-230xe2x80x9d, xe2x80x9cD-400xe2x80x9d, xe2x80x9cD-2000xe2x80x9d and xe2x80x9cT-403xe2x80x9d, sold by Texaco Chemical Company, Houston, Tex.), polytetramethyleneoxide-di-p-aminobenzoates (such as the family of such products sold by Air Products, Allentown, Pa., under the trade name xe2x80x9cVersalinkxe2x80x9d e.g., xe2x80x9cVersalink P-650xe2x80x9d), and the like. Preferred maleimide resins of Formula III include stearyl maleimide, oleyl maleimide, behenyl maleimide, 1,20-bismaleimido-10,11-dioctyl-eicosane (which likely exists in admixture with other isomeric species produced in the ene reactions employed to produce dimer acids from which the bismaleimide is prepared, as discussed in greater detail elsewhere in this specification), and the like, as well as mixtures of any two or more thereof.
In preferred embodiments of the present invention, when mixtures of bismaleimides and divinyl compounds are employed, either Xxe2x80x2 (of the bismaleimide) or Y (of the divinyl compound) can be aromatic, but both Xxe2x80x2 and Y are not both aromatic in the same formulation. Additionally, in preferred embodiments of the present invention, when mixtures of bismaleimides and divinyl compounds are employed, at least one of Xxe2x80x2 or Y is a high molecular weight branched chain alkylene species having from about 12 to about 500 carbon atoms.
Bismaleimides can be prepared employing techniques well known to those of skill in the art. The most straightforward preparation of maleimide entails formation of the maleamic acid via reaction of the corresponding primary amine with maleic anhydride, followed by dehydrative closure of the maleamic acid with acetic anhydride. A major complication is that some or all of the closure is not to the maleimide, but to the isomaleimide. Essentially the isomaleimide is the dominant or even exclusive kinetic product, whereas the desired maleimide is the thermodynamic product. Conversion of the isomaleimide to the maleimide is effectively the slow step and, particularly in the case of aliphatic amides, may require forcing conditions which can lower the yield. Nevertheless, in the case of a stable backbone such as that provided by a long, branched chain hydrocarbon (e.g., xe2x80x94(CH2)9xe2x80x94CH(C8H17)xe2x80x94CH(C8H17)xe2x80x94(CH2)9xe2x80x94), the simple acetic anhydride approach appears to be the most cost effective method. Of course, a variety of other approaches can also be employed.
For example, dicyclohexylcarbodiimide (DCC) closes maleamic acids much more readily than does acetic anhydride. With DCC, the product is exclusively isomaleimide. However, in the presence of suitable isomerizing agents, such as 1-hydroxybenzotriazole (HOBt), the product is solely the maleimide. The function of the HOBt could be to allow the closure to proceed via the HOBt ester of the maleamic acid (formed via the agency of DCC) which presumably closes preferentially to the maleimide. However, it is unclear why such an ester should exhibit such a preference. In any case, it is demonstrated herein that isomide generated by reaction of the bismaleamic acid of 10,11-dioctyleicosane with either acetic acid anhydride or EEDQ (2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline) is isomerized to the bismaleimide by catalytic amounts of HOBt. 3-Hydroxy-1,2,3-benzotriazine-4-one appears to be at least as effective as HOBt in effecting this isomerization, whereas N-hydroxysuccinimide is substantially less so.
Likely, isomerizing agents such as HOBt add to the isoimide to yield the amic acid ester. If this exhibits any tendency whatsoever to close to the imide, much less a strong bias for doing so, a route for interconverting isoimide and imide is thereby established and the thermodynamic product, imide, should ultimately prevail. Thus if the initial closure of ester formed in the DCC reaction yields any isoimide, or if any isoimide is produced by direct closure of the acid, the situation will be subsequently xe2x80x9ccorrectedxe2x80x9d via conversion of the isoimide to the imide by the action of the active ester alcohol as an isomerizing agent.
One problem encountered with bismaleimides is a proclivity for oligomerization. This oligomerization is the principle impediment to yield in the synthesis of bismaleimides, and may present problems in use. Radical inhibitors can mitigate this potential problem somewhat during the synthesis but these may be problematic in use. Fortunately, oligomer may be removed by extracting the product into pentane, hexane or petroleum ether, in which the oligomers are essentially insoluble.
Thermosetting resin compositions of the invention also contain in the range of 0.2 up to 3 wt % of at least one free radical initiator, based on the total weight of organic materials in the composition, i.e., in the absence of filler. As employed herein, the term xe2x80x9cfree radical initiatorxe2x80x9d refers to any chemical species which, upon exposure to sufficient energy (e.g., light, heat, or the like), decomposes into two parts which are uncharged, but which each possesses at least one unpaired electron. Preferred as free radical initiators for use in the practice of the present invention are compounds which decompose (i.e., have a half life in the range of about 10 hours) at temperatures in the range of about 70 up to 180xc2x0 C.
Exemplary free radical initiators contemplated for use in the practice of the present invention include peroxides (e.g., dicumyl peroxide, dibenzoyl peroxide, 2-butanone peroxide, tert-butyl perbenzoate, di-tert-butyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, bis(tert-butyl peroxyisopropyl)benzene, and tert-butyl hydroperoxide), azo compounds (e.g., 2,2xe2x80x2-azobis(2-methyl-propanenitrile), 2,2xe2x80x2-azobis(2-methylbutanenitrile), and 1,1xe2x80x2-azobis(cyclohexanecarbonitrile)), and the like. Peroxide initiators are presently preferred because they entail no gas release upon decomposition into free radicals. Those of skill in the art recognize, however, that in certain adhesive applications, the release of gas (e.g. N2) during cure of the adhesive would be of no real concern. Generally in the range of about 0.2 up to 3 wt % of at least one free radical initiator (based on the total weight of the organic phase) will be employed, with in the range of about 0.5 up to 1.5 wt % preferred.
Thermosetting resin compositions of the invention possess a variety of physical properties making them particularly adapted for use in the preparation of xe2x80x9csnapxe2x80x9d cure adhesives. Such adhesives are useful, for example, in die attach applications. When used in adhesive applications, it is desirable to add coupling agent(s) to the formulation.
As employed herein, the term xe2x80x9ccoupling agentxe2x80x9d refers to chemical species that are capable of bonding to a mineral surface and which also contain polymerizably reactive functional group(s) so as to enable interaction with the adhesive composition. Coupling agents thus facilitate linkage of the adhesive composition to the substrate to which it is applied.
Exemplary coupling agents contemplated for use in the practice of the present invention include silicate esters, metal acrylate salts (e.g., aluminum methacrylate), titanates (e.g., titanium methacryloxyethylacetoacetate triisopropoxide), or compounds that contain a copolymerizable group and a chelating ligand (e.g., phosphine, mercaptan, acetoacetate, and the like). Generally in the range of about 0.1 up to 10 wt % of at least one coupling agent (based on the total weight of the organic phase) will be employed, with in the range of about 0.5 up to 2 wt % preferred.
Presently preferred coupling agents contain both a co-polymerizable function (e.g., vinyl moiety, acrylate moiety, methacrylate moiety, styrene moiety, cyclopentadiene moiety, and the like), as well as a silicate ester function. The silicate ester portion of the coupling agent is capable of condensing with metal hydroxides present on the mineral surface of the substrate, while the co-polymerizable function is capable of co-polymerizing with the other reactive components of invention adhesive composition. Especially preferred coupling agents contemplated for use in the practice of the invention are oligomeric silicate coupling agents such as poly(methoxyvinylsiloxane).
In addition to the incorporation of coupling agents into invention adhesive compositions, it has also been found that the optional incorporation of a few percent of the precursor bismaleamic acid greatly increases adhesion. Indeed, good adhesion is retained even after strenuous exposure to water.
Adhesive compositions of the invention possess a combination of physical properties believed to be critical to successful commercial application:
1. The adhesive compositions have good handling properties, needing little, if any, inert diluent added thereto (i.e., the resin compositions form 100% reactive systems of sufficiently low viscosity);
2. The adhesive compositions are capable of rapid (xe2x80x9csnapxe2x80x9d) cure, i.e., curing in two minutes or less (preferably as short as 15 seconds) at xe2x89xa6200xc2x0 C.;
3. The resulting thermosets are stable to at least 250xc2x0 C., wherein xe2x80x9cstablexe2x80x9d is defined as less than 1% weight loss at 250xc2x0 C. when subjected to a temperature ramp of 10xc2x0 C./min. in air via thermogravimetric analysis (TGA);
4. The resulting thermosets are sufficiently flexible (e.g., radius of curvature  greater than 1.0 meter for a 300 mil2 silicone die on a copper lead frame using a cured bond line xe2x89xa62 mils) to allow use in a variety of high stress applications;
5. The resulting thermosets exhibit low-moisture uptake (in nonhermetic packages); and
6. The resulting thermosets exhibit good adhesion to substrates, even after strenuous exposure to moisture.
Adhesive compositions of the invention can be employed in the preparation of die-attach pastes comprising in the range of about 10 up to 80 wt % of the above-described thermosetting resin composition, and in the range of about 20 up to 90 wt % filler. Fillers contemplated for use in the practice of the present invention can be electrically conductive and/or thermally conductive, and/or fillers which act primarily to modify the rheology of the resulting composition. Examples of suitable electrically conductive fillers which can be employed in the practice of the present invention include silver, nickel, copper, aluminum, palladium, gold, graphite, metal-coated graphite (e.g., nickel-coated graphite, silver-coated graphite, and the like), and the like. Examples of suitable thermally conductive fillers which can be employed in the practice of the present invention include graphite, aluminum nitride, silicon carbide, boron nitride, diamond dust, alumina, and the like. Compounds which act primarily to modify rheology include fumed silica, alumina, titania, high surface area smectite clays, and the like.
In accordance with yet another embodiment of the present invention, there are provided assemblies of components adhered together employing the above-described adhesive compositions and/or die attach compositions. Thus, for example, assemblies comprising a first article permanently adhered to a second article by a cured aliquot of the above-described adhesive composition are provided. Articles contemplated for assembly employing invention compositions include memory devices, ASIC devices, microprocessors, flash memory devices, and the like.
Also contemplated are assemblies comprising a microelectronic device permanently adhered to a substrate by a cured aliquot of the above-described die attach paste. Microelectronic devices contemplated for use with invention die attach pastes include copper lead frames, Alloy 42 lead frames, silicon dice, gallium arsenide dice, germanium dice, and the like.
In accordance with still another embodiment of the present invention, there are provided methods for adhesively attaching two component parts to produce the above-described assemblies. Thus, for example, a first article can be adhesively attached to a second article, employing a method comprising:
(a) applying the above-described adhesive composition to said first article,
(b) bringing said first and second article into intimate contact to form an assembly wherein said first article and said second article are separated only by the adhesive composition applied in step (a), and thereafter,
(c) subjecting said assembly to conditions suitable to cure said adhesive composition.
Similarly, a microelectronic device can be adhesively attached to a substrate, employing a method comprising:
(a) applying the above-described die attach paste to said substrate and/or said microelectronic device,
(b) bringing said substrate and said device into intimate contact to form an assembly wherein said substrate and said device are separated only by the die attach composition applied in step (a), and thereafter,
(c) subjecting said assembly to conditions suitable to cure said die attach composition.
Conditions suitable to cure invention die attach compositions comprise subjecting the above-described assembly to a temperature of less than about 200xc2x0 C. for about 0.25 up to 2 minutes. This rapid, short duration heating can be accomplished in a variety of ways, e.g., with an in-line heated rail, a belt furnace, or the like.
In accordance with a still further embodiment of the present invention, there is provided a method for the preparation of bismaleimides from diamines. The invention synthetic method comprises:
adding diamine to a solution of maleic anhydride,
adding acetic anhydride to said solution once diamine addition is complete, and then allowing the resulting mixture to stir overnight, and thereafter
treating the resulting reaction mixture with a suitable isomerizing agent.
Diamines contemplated for use in the practice of the present invention include saturated and unsaturated dimer diamines (such as the dimer amines sold by Henkel Corporation, Ambler, Pa., under the trade name xe2x80x9cVersamine 552xe2x80x9d and xe2x80x9cVersamine 551xe2x80x9d), xcex1,xcfx89-aminopropyl-terminated polydimethyl siloxanes (such as xe2x80x9cPS510xe2x80x9d sold by Hxc3xcls America, Piscataway, N.J.), polyoxypropylene amines (such as xe2x80x9cD-230xe2x80x9d, xe2x80x9cD-400xe2x80x9d, xe2x80x9cD-2000xe2x80x9d and xe2x80x9cT-403xe2x80x9d, sold by Texaco Chemical Company, Houston, Tex.), polytetramethyleneoxide-di-p-aminobenzoate (such as the family of such products sold by Air Products, Allentown, Pa., under the trade name xe2x80x9cVersalinkxe2x80x9d e.g., xe2x80x9cVersalink P-650xe2x80x9d), and the like. Diamine and maleic anhydride are typically combined in approximately equimolar amounts, with a slight excess of maleic anhydride preferred. Isomerizing agents contemplated for use in the practice of the present invention include 1-hydroxybenzotriazole, 3-hydroxy-1,2,3-benzotriazine-4-one, 1-hydroxy-7-azabenzotriazole, N-hydroxysuccinimide, and the like.